Bone disease in patients with long-term renal transplantation and normal renal function

Renal osteodystrophy may persist during the early years after renal transpl antation. However, information on bone status after a successful long-term renal transplantation is limited. We examined biochemical parameters, bone mineral density (BMD), and bone histomorphometry in 25 asymptomatic men wit h normal renal function after 7.5 +/- 5.7 years of a renal transplantation. Serum calcium, phosphorus, alkaline phosphatase, and 1,25(OH)(2)D-3 levels and urinary calcium level and cyclic andenosine monophosphate excretion we re within normal range in all patients. Serum intact parathyroid hormone (P TH) level was elevated in 11 subjects (133.6 +/- 78 pg/mL) and normal in th e other 14 subjects (47.9 +/- 13.6 pg/mL). Mean BMD at the lumbar spine and femoral neck was low in the entire group. However, it progressively increa sed as time after transplantation increased, approaching normal values afte r 10 years. Bone histomorphometric analysis showed bone resorption, osteoid volume, and osteoid surface greater than normal range in the majority of p atients. Bone formation rate and mineralization surface were low, and miner alization time was delayed in most patients. These lesions were more severe in patients after 3 to 4 years of transplantation but improved with time a nd approached normal values after a period of 10 years. PTH values did not correlate with bone histological characteristics or BMD. These results show that the bone alterations observed after long-term renal transplantation c onsist of a mixed bone disease in which features of high bone turnover coex ist with altered bone formation and delayed mineralization. These findings may result from the combined effect of preexisting bone disease and immunos uppressive therapy. (C) 2000 by the National Kidney Foundation, Inc.